Continue integrating the ground water hydrology work into CABLE #379
Description
This pull request continues integrating the ground water hydrology work of Mengyuan Mu into CABLE, which is taking place in a sequence of pull requests.
PLEASE do not delete any of my in-code comments (tagged rk4417) for now. Once the integration of the ground water hydrology work is complete and its functionality is confirmed to reproduce the results obtained already outside of the repo, I will clean-up all of my comments in a single pull request. Deleting any of my comments now will just make it much more difficult for me to track down and fix any issues that might arise during this process.